Introduction

Dino track!

The Dino Track is a simple
“one channel” Radio Controlled vehicle that was
offered for sale by Radio Shack one Christmas season. After the season
(way after) I bought one stores remaining stock for $4 each ($20 for
five of them). The idea was to convert them into “prey” robots for a
predator/prey experiment in artificial life.

The Dino’s however have two problems, one is that they are not very sturdy
and the second is that the treads on these toys slip on the wheels rather
than move when the weight is too great. This pretty much made them a
non-starter until another member of the San Francisco robotics group
showed how he had fixed the latter problem by gluing tread “grippers”
in the wheels.

The treads do have little “nubs” that hang down and go into a groove on
the wheel which helps, but doesn’t prevent, the tracks from coming off. By
gluing small blocks of plastic, evenly spaced in the drive wheel’s groove,
the drive wheel is able to grab the nubs and force the track along.

I used a Lego wheel attached to the top wheel of the DinoTrack’s drive
system to create an encoder.

Lego Encoder Wheel

When the holes in the wheel pass the detector a pulse is generated. This
is cleaned up by a schmidt-trigger buffer and fed into the input capture
pins of a 68HC11 MCU.

The robot I eventually built is shown below. It used a
Miniboard for control, but the motors were
overheating the L293D so I used the L298 on a daughter card to up the
current capacity of the H-bridge.

Image 1: The Modified Dino Track

One of the more interesting aspects of doing this project was that
I reverse engineered the schematic for the receiver. There is a
copy here in PDF format.
From this I learned that the receiver was simply an oscillator
acting as a tone detector driving an H-bridge. I later took
one of the Dino’s receiver boards and modified it to provide
a remote pushbutton capability. This was accomplished by wiring up half
the H-bridge such that when the button was pressed, the “output” saw 5V
and when the button wasn’t pressed on the transmitter the output saw
“ground.” This could be fed right into an input pin on the Miniboard
and provide a remote signal. As part of the predator/prey experiment
that signal was “you’re dead.”